This invention relates to a rotating magnetic head system for a video tape recorder (VTR) and in particular to a multiplex recording and erasing rotating magnetic head system for multiply recording audio and video signals.
In general for a VTR it is known that 2 heads exclusively used for recording audio signals are mounted on a rotating drum and that FM audio signals are recorded, superposedly on video signals in the recording tracks on the tape (Japanese patent unexamined publication, JP-A-59-142703). Recently a development of incorporating a VTR and camera has occurred and a demand to reduce the size of the development has become strong. In order to respond to this demand, it is known that, as disclosed in Japanese patent unexamined publication JP-A-60-22705, n video signal recording/reproducing magnetic heads (n.ltoreq.4) are mounted on a small diameter rotating drum at equal intervals (360.degree./n), that a magnetic tape is wound on the rotating drum at least over a region of 360.degree..times.{(n-1)/n}and that the video signals are recorded/ reproduced while switching over from one to another of the video signal recording/reproducing magnetic heads, every time that region has been scanned. On the other hand a small size VTR has been strongly desired, which has a small diameter rotating drum including a magnetic head exclusively used for erasing mounted on the rotating drum so as to be provided with the flying erase function apart from recording the FM audio signals.
According to the prior art techniques, if it is desired to add the FM audio multiplex recording function to the small diameter head drum device, 4 video magnetic heads are necessary by the technique disclosed in JP-A-60-22705. Further 4 audio magnetic should be added thereto so that the technique described above can be applied to the FM multiplex recording technique disclosed in JP-A-59-142703. Further, in order that the device having the functions stated above can have the flying erase function, another rotating erasing head having a function to erase a wider width area extending over 4 tracks should be added, and therefore 9 magnetic heads are necessary in total. When the small diameter rotating head drum technique disclosed in JP-A-60-22705 is applied to the VHS system, if the number heads is 4, the diameter of the rotating drum is 41.3 mm. When the audio magnetic heads are added to such a small diameter rotating drum device and further a rotating erasing head is provided, it is difficult to fabricate it from the view point of the space. Additionally the number of parts increases, which decreases remarkably the productivity of the small diameter drum device and in addition it increases the cost.